1. Field of the Invention
The present invention relates to ammunition for shotguns and, more particularly, to a sabot for a shotgun shell capable of enhancing shot dispersion.
2. Discussion of the Prior Art
Conventional shotgun shells are designed to produce relatively large and highly dispersed shot patterns at ranges of engagement typical of sporting applications. Such engagements vary from a short range of approximately 20 meters, typical of upland game shooting, to extreme ranges of 40 to 50 meters, typical of water fowling.
Law enforcement agencies have endeavored to exploit the advantages of large shot patterns available from such weapons to improve the effectiveness of law enforcement personnel engaged in close-range anti-personnel actions. Current technology, however, has not produced a shot shell and weapon capable of providing a high dispersion of shot at the short ranges required. Shooting engagement ranges for such operations are usually on the order of 5 to 15 meters, where conventional shot dispersion pattern diameters range from approximately 5 to 20 centimeters. These small diameter patterns do not materially enhance the probability of hitting the personnel target. In fact, single projectile, burst fire and semi-automatic weapons are becoming more popular due primarily to the ability of such weapons to produce a large dispersion pattern of shots.
A typical prior art shotgun shell 20 is illustrated in FIG. 1 and includes a shell casing 22 with a propellant charge 24 disposed therein adjacent a primer 26 at a rear end of the shell and a sabot 28 filled with shot pellets 30 disposed at an opposite, forward end of the shell. Sabot 28 includes a circular base 32 and a hollow cylindrical portion 34 extending from a peripheral edge of the base toward the forward end of the shell. Shot pattern or, in other words, the shape and size of the area occupied by flying shot pellets, is dictated primarily by the construction of the sabot, which is normally designed to produce relatively high dispersion for medium and long range engagements only. The sabot is often formed with a collapsible buffer 36 disposed between the base of the sabot and the propellant charge to assist in forming a uniform, and preferably spherical, shot pattern by absorbing the shock associated with combustion of the propellant charge.
When a conventional shotgun shell is loaded into a gun and fired, the sabot 28 is propelled forward with the shot pellets 30, as shown in FIG. 2, by expansion of the propellant gases 37. Since the sabot 28 and pellets 30 are confined within a gun barrel 38, they are constrained from expanding radially and are moved in an axial direction only. When the sabot 28 emerges from the gun barrel, however, the radial constraint of the barrel is released and the flight of the shot pellets is then influenced primarily by aerodynamic drag and interactions between the shot pellets and the sabot as shown in FIG. 3. In general, the design of the sabot is such that the dispersion of the shot pellets is delayed; and, consequently, the resulting shot pattern is too small to materially enhance the probability of hitting a personnel target at close range.
U.S. Pat. Nos. 5,189,251, 5,191,168 and 5,192,830 to Puckett, which are incorporated herein by reference, disclose sabots for producing high-dispersion shotgun shells, the sabots including recessed portions extending from the base of the sabot into the shot pellets. When a shell carrying such a sabot is fired from a gun, propellant gases are communicated with the recessed portion of the sabot and will tend to expand radially outward when the sabot exits the gun barrel at the muzzle, thereby imparting a radial velocity component to the pellets and accelerating the dispersion of the shot pellets to form relatively large shot patterns at close-range. These patents also disclose sealing gas producing energetic materials, such as gun powder, within the recessed portion of the sabot using a combustible plug. A disadvantage of the former concept is that the internal pressure of the gases within the recessed portion is limited to the pressure of the propellant gases at the gun muzzle, which is typically too low for optimal expansion. The latter concept provides higher internal gas pressure but requires precision timing of the combustion of the plug tailored to the length of the gun barrel.